leaf spring mount for suicide suspension?

[meteorman]

I am working on setting up a transverse suicide spring for my front end. I am using a 78 dodge motorhome front axle. How do I need to mount the spring to the axle? do I need a perch and shackles?? why do I need this if I do?

Can I just get a spring perch and put the spring on it directly? or do I need a shackle?

Or, can I just bracket the spring down onto the axle directly without a perch and shackle???? why or why not?

thanks in advance.

 

[sgtpontiac]

Not that I'm an expert on suicide axles

I am working on setting up a transverse suicide spring for my front end. I am using a 78 dodge motorhome front axle. How do I need to mount the spring to the axle? do I need a perch and shackles?? why do I need this if I do?

Can I just get a spring perch and put the spring on it directly? or do I need a shackle?

Or, can I just bracket the spring down onto the axle directly without a perch and shackle???? why or why not?

thanks in advance.

the shakles are there to allow the spring to flex....otherwise it would bind so some sort of shakle would be required I would guess.. mounting wise, anything that would securely mount the spring to to a stationary part of the frame should be cool..... remember, this is certainly not my field of expertise....

 

[meteorman]

new question

I think I'm getting why the shackle is necessary, for flex.

next question:
can I mount my spring in one of the side holes on the axle? I have four holes where the old style parallel spring mounted with brackets. Now I don't need those holes, but there is no center hole, and I'm afraid if I drill one, there won't be enough axle left around the hole for strength. So, can I put the spring perch in the hole closest to the vehicle? off-center? and the radius rod will hold it stable.??????
Ugh, thanks for being patient.[S[S

meteorman

 

[kouki]

most people using that type of axle will build a plate that bolts to those 4 holes and make mounts for spring and radius arms, like a batwing.

There are pics in a thread just down the list from this one, I think the title is "suicide perch"

 

[burnin#2]

i am using the same type of front axle as you and i kinda have my own take on the design.... its not done yet and may need some finess.. i will run a cummins with a 5 speed, which is heavy and i just got trailer springs from princess auto. and i am going to double them up for capacity..... check it out for ideas

i since the pics mad up brackets that bolt to each origional spring perch and use a shackle on the left and right side. the radius arm connects to the brackets i made under the axle with a horizontal piviot and im hoping that the leaf spring will keep my caster angle good
like i said this is in the works and just for ideas
good luck, there is a few guys here that are using this style of axle just do some searching and you can find lots of examples

 

[sgtpontiac]

I think burnin and Kouki have it....

either set up will work.... use the exsisting spring perch as the mounting point for the spring eyes/shackles and mount the spring like in burnin's photos in the middle of the frame..... I think those are both good examples...
JMHO

 

[Sam_Fear]

the radius arm connects to the brackets i made under the axle with a horizontal piviot and im hoping that the leaf spring will keep my caster angle good

I don't think that is safe. I'm not real up on front end geometry, so you might want to run that idea by some of the guys here that do know their stuff. What I'm seeing is, at worst, it will rip your shackles apart when you hit the brakes, and at best your caster will be constantly changing because the shackles aren't designed to stress that way.

 

[Blue Eyed Devil]

burnin#2 - The spring will NOT hold your caster! Please take the time to rethink and redesign your entire mockup. Do your research & homework. There are plenty of ways to do what you are trying to attempt, but you're coming up a little short in your execution. Lots of unsafe stuff going on there!

 

[sgtpontiac]

The guys in the know about this stuff have spoken....

I'd pay attention.... they know better than I, theory seemed sound but if they say not, I believe them..... do you have radius rods going out to front axle from the frame? If so, I thought those were for holding the caster angle... not the spring? Like I said, they have done this stuff before and I have not so they are the experts.... IFS I'm better prepared to help with..... Sorry, my bad about saying they were ok..... I'll bow to the masters on this one.... don't want to suggest anything that would be unsafe....

 

[dmw56]

burnin#2 - The spring will NOT hold your caster! Please take the time to rethink and redesign your entire mockup. Do your research & homework. There are plenty of ways to do what you are trying to attempt, but you're coming up a little short in your execution. Lots of unsafe stuff going on there!

My thought too! I'd cut that front end off and start over. Those radius rods are a bad design and that front perch is way to high. Do you know what scrub line is?

 

[Tim...Ok]

Meteorman, check out the pics on page 2 in this link to Scooter67's build thread..This is a very common way to do the brackets to mount the shackle and radius rods..it works and is safe.. thanks for the pics Scooter!!

http://ratrodsrule.com/forum/showthread.php?t=18614

Burnin#2, I would suggest Z'ing that frame or better yet build one from scratch to minimize that front perch..A cummins is about 900 lbs I believe,and the spring IS NOT going to maintain your caster..Like others have said, lots of unsafe going on in those few pics..

Tim

 

[ratdog]

Yes that looks very scary to me also, specially with an engine that weighs twice as much as what most guys use. I would not use a suicide perch set up with that engine at all.

 

[King Herald]

i am using the same type of front axle as you and i kinda have my own take on the design.... its not done yet and may need some finess.. i will run a cummins with a 5 speed, which is heavy and i just got trailer springs from princess auto. and i am going to double them up for capacity..... check it out for ideas.....

.......i made under the axle with a horizontal piviot and im hoping that the leaf spring will keep my caster angle good.....

This is scary dude!

All that weight on a skinny tubular spring perch? All that weight and you also want the torque from the front brakes located by the spring alone??? Best guess it'll bend the tubes, springs and shackles when braking. Worst guess is it'll rip apart and dump your car on the road.

It looks like your chassis rails are upside down too, for some reason.

Seriously, no offence, but re-think the plan and go with something a little more 'conventional', by hot rod building standards.

It is good to be different, but different is not always good.

 

[sgtpontiac]

reference the scrub question.. did you mean scrub radius?

If you mean scrub radius probably easier to state it as the path that the front tire takes when the vehicle / axle is static. Stopped. I know that doesn't make sense but it is a term used mostly (more so) with solid / straight axle vehicles... kind of measures how the road is going to push back against the tire/axle/vehicle.... normally you are simply concerned with toe, caster and camber.... scrub radius sort of sorts itself out if you have the those items set properly for your vehicle... for the most part unless your caster and toe are way out of the norm your scrub radius will be oky doky.... another physic's question..lol ..[S
Hey, so I could be sure I just asked a buddy who is big into building off road vehicles if he knew what scrub was.. here is his response:
scrub is the action of the tire moving / rolling forward saying straight up and down through the arch of the suspension travel. ... not sure if this helps much.....

 

[sgtpontiac]

Sorry dmw....

I am getting old, I thought that Meteorman was asking... you were asking him if he knew.... sorry.... my bad again....

 

[dmw56]

That's OK it comes with age! LOL

Scrub line is an imaginary line drawn from the bottom of each wheel and nothing from the frame or suspension can be below this line. In the event of a tire blow out the suspension parts and frame will not contact the road.

 

[sgtpontiac]

I like your's better....

That's OK it comes with age! LOL

Scrub line is an imaginary line drawn from the bottom of each wheel and nothing from the frame or suspension can be below this line. In the event of a tire blow out the suspension parts and frame will not contact the road.

not so darn complex.....lol

 

[meteorman]

bracket

thanks for the input all. I am thinking I'll use a bracket like Scooter 67 that has a radius rod mount on it and wraps under to the bottom of the axle, if that makes sense? I think I can figure it out. Picked up some scrap steel and will work on fabricating that this week.
I ordered spring pivot and shackles from speedway. should be here next week. then I'll go to the trailer supply shop and order a 2000lb rated leaf spring that's the right length, or custom order one at a local manufacturing shop in Portland. seems like the trailer spring option is cheaper and will work fine.

 

[skull]

figured it out

sounds like your'e gettin' it figured out.

sent pm.

Later

 

[Tim...Ok]

I need to get pics of mine, but i also used a trailer spring for it..I had to turn about .040 off of the OD of the shackle bushings to fit in the eye of the spring after knocking out the cheesy bushing that comes in the trailer spring..could do it on a belt sander if you were careful..good luck

Also, I drew up the brackets I needed and sent them to a local shop, they supplied the 3/8" steel and laser cut them for $40..just FYI